Tuesday, May 09, 2006

Plants don't absorb more heat-trapping carbon dioxide at higher atmospheric CO2 levels because much of the world's soils don't contain enough nitrogen levels. A recently concluded six year study by Peter B. Reich, a forest resources professor at the University of Minnesota highlights a flaw in worldwide computer modeling based on the assumption that plants would take up a good portion of the extra carbon dioxide mankind is emitting into the atmosphere. The study concluded that for plants to absorb extra carbon dioxide, they would need artificially higher nitrogen soil levels, impractical on a worldwide scale: Source: :::[Pioneer Press]

"This suggests a less optimistic scenario for how much of the elevated CO2 the plant systems can soak up,'' said Reich, a professor in the department of forest resources.

...

The researchers did their study by tending 296 field plots containing different numbers and combinations of perennial grassland species. They subjected each to one of four conditions: some got added soil nitrogen, others got added atmospheric carbon dioxide, and still others got added levels of each. The rest got standard levels of nitrogen and carbon dioxide.

Researchers measured the amount of plant material produced in each setting. After four to six years, plots receiving more nitrogen absorbed at least three times as much extra carbon under higher carbon-dioxide conditions than did plots without any extra nitrogen.

Climate modelers will have to revise the assumption, and policy makers need to take note that climate change will be more extreme than earlier predicted. Finally this puts the kibosh on the tactic of the global warming denial crowd who say the carbon dioxide rich atmosphere will be good for plant growth when eventully forced to admit to warming.